In recent years, there is proposed a sole having island-like portions obtained by dividing a front foot portion of the shoe sole in the front-rear or medial-lateral direction (for example, the first and second patent documents identified below). Such a sole is easily bent along grooves between the island-like portions.
[First Patent Document] WO 2006/038338 A1
[Second Patent Document] WO 2004/066771 A1
The third patent document identified below discloses a resilient member extending across a sole groove in a front foot portion for reinforcement. The resilient member is placed between the mid sole and the outer sole, and is attached to the lower surface of the mid sole.
[Third Patent Document] Japanese Laid-Open Patent Publication No. 2001-70004
The fourth to sixth patent documents identified below disclose a sole element that connects between the front foot portion and the rear foot portion along the medial side and/or the lateral side. The sole element may regain the energy used for the deformation of the sole.
[Fourth Patent Document] Japanese Laid-Open Patent Publication No. 2000-225002
[Fifth Patent Document] U.S. Pat. No. 6,199,303 B1
[Sixth Patent Document] U.S. Pat. No. 6,477,791 B2
The seventh patent document identified below discloses a sole including a plurality of columnar leg portions in the rear foot portion. In this sole, the leg portions are connected together by a plate provided on the upper surface of the outer sole separate from the mid sole.
[Seventh Patent Document] US 2004/0181969 A1
In the eighth patent document identified below, an outer sole being a wear resistant reinforcement member is provided across a groove in the front foot portion. Such an outer sole will suppress the bending of the sole along the groove.
[Eighth Patent Document] Japanese Laid-Open Patent Publication No. 2004-65978